(a) Field of the Invention
The present invention relates to a torque converter in a vehicle, which allows a lock-up clutch to be put into operation while sufficiently attenuating vibration at all rotation speed ranges of a low rotation speed range to a high rotation speed range of an engine.
(b) Description of the Related Art
In general, a torque converter is mounted between an engine and a transmission of a vehicle for transmission of driving power from the engine to the transmission by using a fluid. The torque converter is provided with an impeller for receiving the driving power from the engine to rotate, a turbine for being rotated by oil being discharged from the impeller, and a reactor (also called a stator) for directing an oil flow returning to the impeller in a rotation direction of the impeller to enhance a torque change rate.
Since power transmission efficiency of the torque converter may be reduced if a load on the engine becomes high, the torque converter has a lock-up clutch (also called a damper clutch) which can directly connect the engine and the transmission. The lock-up clutch is arranged between a front cover directly connected to the engine and the turbine for direct transmission of the torque from the engine to the transmission through the turbine.
The lock-up clutch includes a piston at a turbine shaft, which is movable in an axial direction. The torque converter is provided with a torsional damper for absorbing vibration and impact acting in a rotation direction when the lock-up clutch is in operation.
Such a related art torque converter has a problem in that, since vibration is intensive when the lock-up clutch is operated at the low rotation speed range of the engine, the lock-up clutch is operated at a high rotation speed range over a certain rotation speed, which causes poor mileage of the vehicle.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.